CN108168441B - Speckle interference three-dimensional dynamic detection system based on time division multiplexing - Google Patents

Abstract

The invention provides a three-dimensional dynamic detection system based on time division multiplexing of speckle interference, which belongs to the technical field of photomechanics. The system includes a laser, a chopper, a CCD camera, a beam splitter, a reflector, and a beam expander. The laser emitted by the laser is divided into two beams by the beam splitter. Once the beam enters the chopper through the beam splitter, it is controlled by the chopper. The reflector enters the beam expander, and after expansion, it shines on the surface of the object; the second beam passes through the dichroic mirror 1 and the reflector 1, enters the chopper, and then passes through the reflector 3, passes through the beam expander 1, and illuminates the surface of the object to be measured; the third beam passes through The beam splitter 1 reflects into the chopper, and is controlled by the chopper to enter the beam expander through the reflector. After the beam is expanded, the beam splitter 4 reflects the beam into the high-speed CCD camera as the reference light for off-plane displacement measurement. The invention integrates the three-dimensional measurement optical path into a set of optical path systems, uses a chopper to realize automatic switching of the optical path, and provides a highly accurate method for real-time detection of dynamic three-dimensional displacement.

Description

Speckle interference three-dimensional dynamic detection system based on time division multiplexing

Technical field

The invention relates to the technical field of photomechanics, and in particular, to a three-dimensional dynamic detection system based on time division multiplexing of speckle interference.

Background technique

Electronic speckle interference technology is a measurement technology based on optical experimental mechanics. It has the advantages of non-contact, high precision and high sensitivity. It can quickly and accurately measure the displacement and strain of the measured part, and can achieve full-field measurement. At present, electronic speckle interference detection technology has been maturely used in the detection of unidirectional displacement or strain, but there are still certain problems in real-time detection of three-dimensional dynamics. Tang Chen of Tianjin University (Tang Chen, Chen Mingming, Su Yonggang, Li Biyuan. A dual-optical path three-dimensional speckle interference system based on a spectroscope, CN106052565A[P].2016.) invented a dual-optical path three-dimensional speckle interference system based on a spectroscope. The interference system uses an energy attenuator to control the laser energy to measure out-of-plane and in-plane displacements. However, this system requires the use of a long-distance microscope and cannot measure three-dimensional dynamic displacement in real time. Gu Guoqing (Gu Guoqing, Wang Yanfang, She Bin. A three-dimensional digital speckle interferometry synchronous measurement method and device, CN105716536A[P].2016.) and others from Yancheng Institute of Technology studied a three-dimensional digital speckle interferometry synchronous measurement system. , two lasers with different wavelengths are required and optical fibers are used for transmission. The three displacement sub-fields obtained by this technology are concentrated on one speckle pattern, and there is mutual coupling. Therefore, subsequent calculations are required to separate the three displacement sub-fields. This This technique often produces large errors. Wang Kaifu of Nanjing University of Aeronautics and Astronautics (Wang Kaifu, Gu Guoqing. Three-dimensional digital speckle interferometry three-field independent, synchronous and real-time measurement method and device, CN103148798A[P].2013) and others studied a three-dimensional digital speckle interferometry three-field independent , Synchronous real-time measurement method, which uses three CCD cameras for collection, has complex equipment and high cost.

Contents of the invention

The technical problem to be solved by the present invention is to provide a three-dimensional dynamic detection system based on time division multiplexing of speckle interference, which adopts the principle of dividing a continuous laser beam into 3000Hz pulse lights for three-dimensional detection respectively, and realizes the three-dimensional displacement of vibrating objects. , vibration frequency, vibration amplitude, etc. are measured simultaneously.

The system includes a laser, a chopper, a CCD camera, a beam splitter, a reflector and a beam expander. The number of the beam splitter, reflector and beam expander is more than one. The laser emits laser and the laser is divided into Two beams, one of which enters the chopper through the spectroscope, enters the beam expander from the reflector under the control of the chopper, and shines on the surface of the object after expansion; the other beam is split by the spectroscope and then passes through it again The beam splitter is divided into two beams, one of which reaches the reflector, is controlled by the chopper to reach the other reflector, and is finally illuminated on the surface of the object to be measured through the beam expander. The other beam after two splits passes through the beam splitter. The reflection enters the chopper, and is controlled by the chopper to enter the beam expander through the reflector. After the beam is expanded, the beam is reflected by the beam splitter to the high-speed CCD camera as the reference light for off-plane displacement measurement.

Commonly used system settings include 3 beam splitters, 8 reflectors and 3 beam expanders. The laser emits laser and splits the laser into two beams through the beam splitter 2. Once the beam enters the chopper through the beam splitter 2, at the end of the chopper Under control, the reflector 4, 6, 7 and 8 enter the beam expander 3, and then shine on the surface of the object after the beam is expanded; the beam 2 passes through the beam splitter 2 and then reaches the reflector 1 through the beam splitter 1. The chopper controls the beam to reach the reflector three, and finally shines on the surface of the object to be measured through the beam expander one; the beam three passes through the beam splitter two and then is reflected by the beam splitter one and enters the chopper, and is controlled by the chopper to pass through the reflector two and Reflector 5 enters beam expander 2. After beam expansion, beam splitter 3 reflects the beam into the high-speed CCD camera as the reference light for off-plane displacement measurement.

Among them, the chopper controls three laser beams to appear alternately, using beam one and beam two to pass through, and beam three is blocked to achieve the measurement of in-plane displacement; beam one and beam three pass, and beam two is blocked to achieve the measurement of out-of-plane displacement.

The synchronization of CCD camera and chopper is realized by PLL speed control circuit.

The beneficial effects of the above technical solutions of the present invention are as follows:

(1) The present invention can realize the measurement of three-dimensional dynamic displacement by using an optical path system of one laser and one camera. Compared with the existing three-dimensional detection optical path system, the present invention has a high degree of integration of optical paths, that is, only one optical path system is needed to solve the measurement in three directions; the structure of the present invention is simpler, uses less equipment, and does not require Three-dimensional dynamic displacement needs to be obtained by adding cameras or lasers.

(2) The present invention measures the displacement in the x, y and z directions in real time by using a chopper to divide a laser beam into four beams. The invention enables real-time measurement to be truly realized without manual switching of optical paths. The measurement results of the present invention will be reflected in different speckle patterns, there is no coupling, and the accuracy is higher.

This system can form a set of equipment that is portable, easy to transport, requires little adjustment, and is ready to use, which is extremely convenient for solving three-dimensional dynamic vibration problems at the inspection site. The present invention puts forward a new idea for solving three-dimensional dynamic real-time detection. The method of using a chopper to realize laser time division multiplexing is original and greatly promotes the development of three-dimensional dynamic detection technology.

Description of drawings

Figure 1 is a schematic diagram of the optical path of the speckle interference three-dimensional dynamic detection system based on time division multiplexing of the present invention;

Figure 2 is a three-dimensional model diagram of the integrated system according to an embodiment of the time-division multiplexing-based speckle interference three-dimensional dynamic detection system of the present invention, in which (a) is the overall appearance diagram and (b) is the internal view.

Among them: 1-laser; 2-beam splitter one; 3-beam splitter two; 4-reflector one; 5-chopper; 6-reflector two; 7-reflector three; 8-reflector four; 9- Reflector five; 10-Reflector six; 11-Reflector seven; 12-Reflector eight; 13-CCD camera; 14-Beam splitter three; 15-Beam expander one; 16-Beam expander two; 17-Expander Beam mirror three; 18-beam one; 19-beam two; 20-beam three.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

The invention provides a three-dimensional dynamic detection system of speckle interference based on time division multiplexing.

As shown in Figure 1, the system includes laser 1, chopper 5, CCD camera 13, 3 beam splitters, 8 reflectors and 3 beam expanders. Laser 1 emits laser and divides the laser into two parts through beam splitter 2 and 3. Two beams, beam one 18 enters the chopper 5 through the beam splitter two 3, and under the control of the chopper 5, it enters the beam expander three through the reflector four 8, the reflector six 10, the seven reflectors 11 and the eight reflectors 12. 17. The beam is expanded and illuminated on the surface of the object; the beam two 19 passes through the beam splitter two 3 and then reaches the reflector one 4 through the beam splitter one 2, and is controlled by the chopper 5 to reach the reflector three 7, and finally passes through the beam expander one 15 Illuminating the surface of the object to be measured; beam three 20 is reflected by beam splitter two 3 after being reflected by beam splitter one 2 and enters chopper 5. It is controlled by chopper 5 and enters the beam expander through reflector two 6 and reflector five 9. 2 16. After the beam is expanded, the beam is reflected by the beam splitter 3 14 into the high-speed CCD camera 13 as the reference light for off-plane displacement measurement.

In the optical path design of the present invention, the test piece is illuminated symmetrically by beam one and beam two. At this time, beam one and beam two pass through the rotation of the chopper blade, and beam three is blocked, and the camera located directly in front of the test piece collects the in-plane displacement. The fringe diagram can calculate the in-plane displacement. When the chopper blade rotates to another position, beam one is used as object light to illuminate the surface of the specimen and is reflected from the surface of the specimen to the camera target surface. Beam three is used as a reference light and is reflected by spectroscope three to the CCD target surface. The interference between the object light and the reference light produces interference fringes, and the off-plane displacement can be obtained through calculation. When the chopper blade rotates to another position, the in-plane displacement in the y direction can be measured, thus realizing the function of real-time detection of dynamic displacement in three directions.

The present invention only requires that the exposure time of the camera is less than the light path switching time, so that when the camera collects the same picture, only light from one optical path enters the camera, that is, the chopper blade cycle can be designed as needed. In one embodiment of the present invention, the chopper speed is designed to be 100 r/s, and there are 10 cycles per week. Each cycle is shared by the three directions of x, y and z, so the switching time of different optical paths is Therefore, the exposure time of the camera must be less than 0.3 ms. An embodiment of the present invention proves that the interference fringe pattern collected at this time is more effective. The detection results of an embodiment of the present invention are compared with the results of a dual-frequency interferometer. The measurement error in the x direction is about 1 μm, the measurement error in the y and z directions is about 0.5 μm, and the amplitude measurement error is about 0.5 μm.

As shown in Figure 2, it is a three-dimensional modeling diagram of an embodiment of the present invention. Figure (a) is the overall appearance of the embodiment of the present invention, and Figure (b) is the internal view of the embodiment of the present invention. The beam expander 1 and the beam expander 2 can measure the in-plane displacement in the y direction. The beam expander 3 and beam expander 4 can realize the measurement of the in-plane displacement in the x direction, and the beam expander 5 and the beam expander 3 and the beam expander 4 can realize the measurement of the out-of-plane displacement in the z direction. In the embodiment of the present invention, the beam expander 5 is selected Use beam expander 3 to achieve measurement.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "x", "y", "z", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention. and simplified description, rather than indicating or implying that the device or component referred to must have a specific orientation and the optical path must be constructed in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (4)

1. A speckle interference three-dimensional dynamic detection system based on time division multiplexing is characterized in that: the device comprises a laser (1), a chopper (5), a CCD camera (13), a spectroscope, a reflecting mirror and a beam expander, wherein the number of the spectroscope, the reflecting mirror and the beam expander is more than one, the laser emitted by the laser (1) is divided into two beams by the spectroscope, one beam enters the chopper (5) by the spectroscope, enters the beam expander by the reflecting mirror under the control of the chopper (5), and irradiates on the surface of an object after being expanded; the other beam is split into two beams by the beam splitter, one beam reaches the reflector, is controlled by the chopper (5) to reach the other reflector, finally irradiates the surface of the object to be measured by the beam expander, the other beam after the two beam splitting enters the chopper (5) through the beam splitter, is controlled by the chopper (5) to enter the beam expander through the reflector, and is reflected into the CCD camera (13) by the beam splitter after the beam expansion to serve as reference light for off-plane displacement measurement.

2. The time division multiplexing-based speckle interference three-dimensional dynamic detection system of claim 1, wherein: the laser beam expander comprises 3 spectroscopes, 8 reflectors and 3 beam expanders, wherein laser emitted by a laser (1) is divided into two beams by the spectroscope II (3), a first beam (18) enters a chopper (5) by the spectroscope II (3), and enters a beam expander III (17) by a reflector IV (8), a reflector VI (10), a reflector seven (11) and a reflector eight (12) under the control of the chopper (5), and the object surface is irradiated after beam expansion; the second beam (19) passes through the second beam splitter (3), then reaches the first reflecting mirror (4) through the first beam splitter (2), reaches the third reflecting mirror (7) under the control of the chopper (5), and finally irradiates the surface of the object to be detected through the first beam expander (15); the beam III (20) is reflected by the beam splitter II (3) and enters the chopper (5) through the beam splitter I (2), the chopper (5) controls the beam to enter the beam expander II (16) through the reflecting mirror II (6) and the reflecting mirror III (9), and the beam is reflected into the CCD camera (13) through the beam splitter III (14) after being expanded to serve as reference light for out-of-plane displacement measurement.

3. The time division multiplexing-based speckle interference three-dimensional dynamic detection system of claim 2, wherein: the chopper (5) controls three laser beams to alternately appear, and the first light beam (18) and the second light beam (19) pass through the chopper, so that the third light beam (20) is blocked to realize the measurement of in-plane displacement; the first light beam (18) and the third light beam (20) pass through, and the second light beam (19) is blocked to realize the measurement of out-of-plane displacement.

4. The time division multiplexing-based speckle interference three-dimensional dynamic detection system of claim 1, wherein: the CCD camera (13) and the chopper (5) are synchronized by a PLL speed control circuit.